Push-pull amplifier for relaxation oscillations



.H. BAHRING PUSH-PULL AMPLIFIER FOR RELAXATION OSCILLATIONS Filed April1, 1937 Patented Apr. 16, 1940 UNITED STATES PATENT OFFHCE PUSH-PULLAMPLIFIER FOR RELAXATION OSCILLATIONS Herbert Bahring,Berlin-Zehlendorf, Germany,

assignor to the firm of Fernseh Aktiengesellschaft, Zehlendorf, nearBerlimrGermany Application April 1, 1937, Serial No. 134,411 In GermanyApril 2, 1936 Claims. (Cl. 250-27) This invention relates toarrangements for Fig. 1 shows a diagram of the push-pull cirsimultaneousamplification of relaxation cscillacuit independent of the relaxationoscillation cirticns and exciting impulses as are used, for incult to beused. Fig. 2 shows an embodiment in stance, in electrical televisiontransmitting and which one of the two push-pull tubes is used as a 6receiving systems for analyzing or synthesizing blocking tube of atwo-tube relaxation circuit. 5 images. Fig. 3 shows a further embodimentin which the The impulses available to control the relaxarid v l a e fpp ph or a ond e i tion oscillations, for instance, frame or line ta enrom a es or in t en 'gTid ead of synchronizing impulses, do mostly nothave the the p fi ube theoretically desired shape, for instance, exactThe tubes l and. 2 in Fig. in this Case are 10' rectangular shape, butare more or less distorted. Screen gTid b o the p t Of which They mayconsist, for instance, of a series of e relttXa-tioh Oscillations are ppin PP short impulses which rise above an irregular in- Site p and 0 theput 5 and of which terference oscillation. Furthermore, they must e x iimp ar pp e i the same be amplified to an amount whjgh makes a, securephase. The plate circuits 0f the tubes are con 15 control of therelaxation circuit possible. If a cted by a load esistor 3 in such amanner that tube of the oscillating circuit was simultaneously theamplified relaxation oscillation may be taken usedfor impulseamplification, these interferfrom 9 and H and the a p fi e C ences wouldalso be amplified and be noticeable P 5 y e taken m 9 and t3, and Hi andon the image. On the other hand, it is not de- H. r s v The r s 8 iscenttit-tapperl-v 2o sirable to provide for an extra amplifier stage forW s g maghetifi deflection, the I'eSiStOI s the exciting impulsesbecause the cost of th substituted by a choke. Aresistor I2 is providedentire set will thereby be increased, in order to compensate fornon-uniformity of the Therefore, it is the object of thi in tio t tubes.A resistor is and a condenser M serve to 25. apply the exciting impulsesin the arne phase to produce the bias for the tubes, and a resistor twoamplifier paths in push-pull, whereas the It makes the adjustment of there id relaxation oscillation voltage is applied in oppo- VOltage p ss Thcondenser H serves as a site phase to these am lifier paths so thatcomcoupling condenser f the yn niz n impensation of the excitingimpulses and their interp se ferences occurs in a load resistance. Ifboth tubes are exactly alike, compensation 30 This arrangement. has theadvantage that the 0f t e exciting impulses applied at 6 and I oosametube may simultaneouslybe used for amcurs also if resistance I2 is notprovided. As the plification of the relaxation oscillation and for e ngrid currents r of pp i h he amplification of the pulses withoutallowing inresulting current variation in the resistor l2, and

terferences in the impulses or the impulses proper thereby t e Variationin Screen grid Voltage 35 to influence the amplified relaxationoscillation. caused by the screen grid relaxation current in Theamplifier tube, which represents one of the is Thus, there is 110eaction of the two amplifier paths, may be used at the same screen gridon the control voltage so that a pure time as blocking tube in atwo-tube reflex resaw-tooth wave will be amplified. In this case,

laxation circuit, the short-circuiting condenser !5 may also be 40 It isa further advantage that impulses of eliminated whereby the inputimpedance of the opposite phase may be obtained between anode impulsecircuit will be increased. If, however, and cathode of both push-pulltubes if the load he tube 5 has a p fi on a or Of #1 and is inductive.These impulses are produced by a plate resistance Rii, and the tube 2has an the saw-tooth shaped voltage at the grid and by mplifi ti n f r f#2 and a p e re istance 45 the voltage produced by the saw-tooth shapedRig, the value R2 of the resistance I2 for intercurrent accordin to thelaw ference compensation will be divided by a tap 8 in a part 11 on theside of tube l, and a part r2 L on the side of the tube 2 in such amanner that These impulses may be used as positive or nega- T (Ri tiveimpulses for the synchronization of further circuits. T1 T2 (Ri Thedrawing shows embodiments of the inven- 55, tion. 3 I J wherein Ra isthe impedance of the resistor 8.

Y I Yi Y Y Y IY In Fig, 2 thepush t-pull circuit is joined with a f I IY I ;two -tube reflex relaxation circuiti Y I Y I Y I Y I Y i Y I i YThe Y push-pull circuit corresponds to that or I I Y I Y Y IFig; l:exceptthat the synchronizing impulses ing of the Y condensers 28, 3E, 35and 35 occurs, Y I Y 1 through the Y devices I 21- and 28. Y Thecharging I I Y I I I I occurs in Y opposite phase Y symmetrically to theY I Y I Y Y cathode of the tubes landZ, which are grounded- I Y Y Y Y YY Y Y Y Y I I I :not applied. :to-the screen igrids of the push+p1n1through the biasdevice l3 and 14; I Avoltage iris I Y I Y Y Y Y Y i:tubes, buttothecontrol grids in thesame phase, Y ing opposite phase isapplied to the grids of Y Y Y Y Y Y Y I by roeansof a resistor Z L- .Thegrid of a discharge; Y the push-pull tubes at the voltage dividing tapsY I Y I I I tube is connected by: condenser 2 3 with the during thecharging :period of: the: condensers; Y I Y I Y Y Y Y I I I I I Y platecircuit f: the tube: The, tuned: serves Y The screen grid: currents andplate currents of Y I Y 1; the periodicaldischarge of the condensers 23,S I I the tubes: l and ,2 also very in O p Phase YSOY Y Y Y 35 and eEhgfging current t k from a Y that the: voltagevariation on thescreengrids; is Y I Y I Y supply source atithe points is and 2e, andflows- Y :nili while the; variation in plate Current will be I Y i Y s mt a v eg ;2a a d gas Ewhichi may, fe r made u sef ul by utilization :ofsawtooth current i Y IY instance; be resistors or saturated diodes whichY inthe: resistancefl, or by tak ng a saw-tnothvo Y Y I allowtheflgvgrofa ub tantially on ta t m t-'5 age from the resistance 8; I Ifboth halves of the I1 I YIYIY u-The relaxation'periodIis started byapnlying a I I I I I 85; I'llhe'amplitude of theiimpulseson the grid oithe p it d v i a nnthe grid 0f tube t n IY Y Y i T I diSGhaIg2 tube:must :lie approximately i to 2 Y I the sridcf: tube l ,Iand:to cause thesamep t m Y I Y i Y IY Y Y Y Y I Y mvoit abov theinoiige level; which isIcamedby Y tial; variationsinthe; plate circuits ofiboth amplii-; i I II I I I I I variations of thevoltage supply; rorinstanee,tne I Y fi r tbes by the ynchroni n imsu s a-p l YI IY I:I: II I:rectifier:arrangement-oiby electrostatic 'or rnag I Y t th sr da r s s4i! and 4|: must have I Y Y Y Y YY Y Y Y f m ,n'eticI interference; Yone charging or the eon- I su hw u s t h mi Y Y Y den'sers 29,35, 35 andIifiover' 2i and 26 is dis- 131G135? Y Y Y Y Y Y Y Y Y Y Y turbed in such a manner that the plate current YY Y Y Y of the tube 5 is stillfurther decreased, and the 2 impulse applied to the grid of the tube 22be m 5 comes still more positive. The condensers 29, 3!, 1= '2 o 3 Y g gfi g 5 5 522255 5 2 3 23?; 5, 2%: The above relationship represented inthe first drop caused by the discharge current in the equation isderived from a consideration of the sistors s2 and s3 aids the backfeed. The tube W tubes Operating in h pllsh'pun amplifica' 22 is notblocked and remains in this condition g of the f S E f F such 0501113"through the period of back feed over the resistors g i ig g gf gi g gg gand respectlvely durmg E dlsclfiarge the relaxation oscillator circuitassociated with 01. Litre clondensiers 29 gi lm ga fz 2 the tube 22. Thederivation of the formula is or 1 en sync as follows. The relaxationoscillation voltage lmplulse p 1s shoQrler than P applied to the grid oftube I is amplified a total charge period. During the discharge periodthe of 2 times where 2 is the amplification factor grid the tube 22becomes strongly positive of the tube taken between the control grid andE 1t w gnd current Durmg the dlscnarge screen grids. It follows, thatthe voltage applied ese electrons flow through the Condenser to thecontrol grid of the tube 2 must equal the After the discharge completedthey Cause a screen grid voltage of tube I divided by the am- 60 gcharge f of f tube so that plification factor ,u., in order to realizethe same thls gnd become g Y blockefi plate voltages in the platecircuits of both tubes. charge of the Pondenser W111 equahze ltself Thetotal effective voltage of screen grid circuit through the resistancethe Condenser the of tube I is divided across a circuit of R1 R'z and 5condenser H and one-half of the resistor 8, ac- Riz in series, f whichR32 is the ht nt f cordmg to thelr F Constants- The resulting resistors4| and 43 in parallel and. constitutes Voltage 011 the and 15 thus not ndependent the portion from which the signal is obtained and on thecharacter of the exterior resistance, but applied t t control grid ofthe tube 2 Hence also upon the time constants of these elements. IFurthermore, they can be shifted by a constant 70 amount by varying thepotentiometer 25. Dur- RI+RI2+RM ing the rise of the curve itsinstantaneous value, from Whlch however, is of such a magnitude that itprevents 13 312 the tube 22 from drawing plate current. Because Y of theblocking of the discharge tube, the charg- The second formula is derivedfrom a consider-'- 1 'I'he condensers 29 and ti; Y and 35 and gdli; re YI Y spectively, form a capacitive voltage divider, the Y Y Y Y Y I tape:of which are connected I with the Y grids of I I I I the tubes I l Iand 2.: I The resistances 24 and: E5

:serve to adjust the discharge period of; the Y con- I "denser Y I Y i YY Y I'he operation of: this circuit is as followsz I Y I Y i Y I Y I I Yi Y I Y I Y Y i Y I Y I change is greater than theirsulse on. the grid;Y i Y Y i i 1 1 Y I Y i Y Y I i I applied to the gi'idi Of thedischarge? tube: 22 Z I Y I Y I Y Y Y by: means of a coupling condenser23; -The d I I charge: tube: 22$ begins I to; draw plate current, I Y

:pull tubes 2 l I and 2 at'the points ii and 3; :This' Y I I I Y Icauses aniincrease in platepotential by the same I I Y I amount or bothtubes I E and 2 so that the d e Y i I I 1 Y 1 I Y Y fleeting systemconnected ;atis and it remains Y Y I 1 I ;uninfluenced. Y 'Ihe change inplate potential in I Y the tube 1 ini respect to its Y cathode, i whichi i Y Y Y :negativeinipulse to the grids of the two push-J lead; of: thetube i.

load resistance 3; are dynamically: coupled; it; is I possible to:swing: both amplifier, tubes in the Y Y Y I non;-linea;r i'ange of, thecharacteristic in I order, I f Y to obtain a resulting saw-tooth curve YY Y I Y If the synchronizing impulse comes to its i end I after thecondenser has started to charge, the Y Y Y Y I alnode; potentials: ofboth tubes -I: and 2; will be i Y Y come more negative b yIthe sameamount, so that I Y I :no Iinterferencein the image Iwiil Ybenoticeable; I The increased negative bias; on: the grid of: the Yblocked: tube 22 has only: the effect of blocking Y I thistabestillmohe; Y :The iength of: duration of I Y I Y the synchronizingimpulse is, therefore; of Y no I Y I Y I impo tancefor theicircuitl i Yi Y I Y Y Y I Y I I Fig 3 shows a circuit in which-the tubes;i and I I YI 2 are not arranged symmetrically; but in: which i Y I Y I Y Y the gridgvoltage of opposite; phase for the Ituhe 2 I Y I I Y is taken from aresistance in I the screen, grid Y Y Y Y Y Y In, order to obtain thesame Y Y so I impulses to obtain a balanced output therefrom,

ation of the two tubes l and 2 operating as amplifiers for thesynchronizing impulses applied to the screen grid of the tube I. Sinceboth tubes are presumed to be identical, the amplification factor 1 oftube 2 taken between the control grid and plate will be the same as theamplification factor of tube I. However, the synchronizing impulses arenot applied to the control grid of tube I, but to the screen grid oftube I, and consequently the amplification factor of tube I with respectto signals applied to the screen grid, will be different and equal to s.Of the signals applied to the screen grid of tube I, a portion thereofwill be applied to the control grid of tube 2, this portion being equalto the ratio of the equivalent resistance 41-1-43 over the sum of thisequivalent resistance the resistance 40 which may be expressed as R?2+R1 where R2=the equivalent resistance of 4:14-43 in parallel andR1=resistance 40. To obtain the same effect in the plate circuits ofboth tubes, the values of R'z and R1 must be such that Simplifying thisequation to obtain a value for R1, one obtains The condenser 42 is acoupling condenser; the condensers 45 and 46 serve as by-pass. Theoperation of the relaxation device formed by the tubes i and 22 isexactly the same as that of the tubes 1 and 22 and the circuit accordingto Fig. 2. The circuit does not require a supplementary plate suppLvsource for generation of the saw-tooth voltage of oposite phase.

I claim:

1. In combination, a source of relaxation oscillations, a source ofcontrol impulses, and common means for simultaneously amplifying saidrelaxation oscillations and said control impulses and applying saidamplified control impulses to said source of relaxation oscillations tocontrol the frequency thereof.

2. In combination, a source of relaxation oscillations, a source ofcontrol impulses, a pair of electron discharge devices, means includingsaid discharge devices for amplifying said control means also includingsaid discharge devices for amplifying said relaxation oscillations toobtain an unbalanced output therefrom, and means connecting one half ofsaid balanced output to said source of relaxation oscillations tocontrol the same. I

3. In combination, a source of relaxation oscillations, a source ofcontrol impulses, a pair of electron discharge devices, means includingsaid discharge devices for amplifying said control impulses in push-pullrelationship to obtain a balanced output therefrom, means also includingsaid discharge devices for amplifying said relaxation oscillations inpush-pull relationship to obtain an unbalanced output therefrom, andmeans connecting one half of said balanced output to said source ofrelaxation oscillations to control the frequency of the same.

4. In combination, a pair of electron discharge devices connected inpush-pull, a condenser charging circuit apportioned equally between theinput circuits of said electron discharge devices, a separate electrondischarge device connected across said input circuits, and having acontrol grid, means for applying impulses to said input circuits inphase to provide amplified impulses in balanced output in the outputcircuits of said push-pull connected discharge devices, and means forconnecting the control grid of said separate device to the outputcircuit of only one of said push-pull connected devices.

5. In combination, a pair of electron discharge devices having outputcircuits connected in pushpull arrangement, a condenser chargingcircuit, means for applying potentials from said charging circuit out ofphase to the input circuits of said electron discharge devices toprovide amplified potentials across the push-pull connected outputcircuits, a separate electron discharge device connected across saidcondenser charging circuit, and having a control grid, means forapplying synchronizing'impulses in phase tosaid input circuits of saidpair of electron discharge devices to provide amplified impulses inbalanced output in the push-pull output circuits of said dischargedevices, and means for connecting the control grid of said separatedevice to only one of said push-pull connected output circuits.

HERBERT BAHRING.

